Power amplifiers (PAs) can be used in many different types of applications. For example, PAs are typically used in wireless devices such as cellular telephones and mobile Internet devices to amplify an outgoing radio frequency (RF) signal to a sufficient power level for transmission, e.g. to a cellular or other wireless network. Such power amplifiers often include one or more gain stages which can be formed of different types of semiconductor devices such as transistors.
In general, it is desirable for the PA to output a signal having a substantially constant gain over a temperature operating range of the device. However, certain PAs can suffer from large gain variations at different temperatures, if not supplied with a temperature dependent bias. As such, it is desirable to limit gain variation as the PA operates at different temperatures. One common method for compensation of gain as temperature changes is to use so-called PTAT currents, which are proportional to absolute temperature, to provide a bias current that increases with temperature. However, this temperature dependent current can negatively impact linearity characteristics of the PA. Thus a need exists for improved control of a PA or other amplifier to reduce gain variation.